Friday, June 1, 2012

Accretionary Wedge #36: How does life affect geology? Surviving on the Colorado Plateau

There was a day this home was abandoned. There was a day that something happened, a decision was made. Were they under attack? Did people die? Or was it a moment that a family knew the crops had failed, and there would be no food that winter? Or no more water in the nearby streambed? Were they called away to another place by a chief, or a shaman? Lots of questions, questions that are hard to answer. But abandoned it was, along with hundreds or thousands of similar homes in the region. Abandoned for hundreds of years before others came into the region.

Tourists seek out these former homes, and many of them remark on the permanence of these structures, still standing after 800 years. I look at them and I think of the permanence of stone, maybe, but also the transitory existence of people and populations. Before the decision to leave, generations of people had lived in these structures, and throughout their lives they never thought of being anywhere else. They didn't plan on enduring whatever catastrophe or threat that led to the decision to leave. But leave they did. There are lots of hypotheses, but I feel pretty strongly that they finally exceeded the capacity of the land to support human populations. That led to whatever else happened, I suspect.

Accretionary Wedge #46, hosted this month by Knowledge Flocs asks the question: How has life or civilization been affected by geology or how has geology been
affected by life? I pondered this question essentially for the whole month before sitting down tonight and writing this. I was out there on the Colorado Plateau a few weeks back, and I almost mindlessly snapped a picture that I didn't give a second thought to. It was part of the view from the Wahweap Overlook at Lake Powell on the border between Arizona and Utah, and I was snapping a series of shots to get sort of a panoramic record of the view.

Tonight it caught my eye. A coal-burning power plant on the shores of an artificial desert lake. What is the carrying capacity of this land? There are thousands of people living in the immediate vicinity, but there are lines of copper wire leading out like a web to literally millions of homes in the wider region, especially places like Phoenix or Las Vegas. Looking at the coal-burning powerplant is to realize that the present-day population is depending on sunlight that fell on plants 70 million years ago to survive. They are depending on water that used to exist only in a deep inaccessible canyon. And to propel their vehicles they import the remains of plankton and one-celled organisms that lived by trillions upon trillions 200 million years ago in oceans and seas that don't even exist on Planet Earth anymore. Their food in large part is grown in other states or other continents.

And we take for granted that we will be living here permanently. We barely ever give thought to the intricate web of connections and imported energy that keeps this civilization alive. What happens when a piece of the web breaks?

I ask in particular because of that white strip along the shoreline of Lake Powell. It's the bathtub ring of the reservoir. It doesn't look like much from my lofty perch, but that is a terrifying lake level if you are one of the watermasters responsible for providing an allotment of water needed to keep things going downstream. The Colorado is the most important source of water in this arid land except for groundwater, which is pretty much non-renewable and is being used up in many areas. The region has been suffering through a decade-long drought, and global warming is leading to changes that may intensify the droughts for the conceivable future.

There are limits.That is the effect of geology on human life in this region. There is only so much water, and there is only so much coal. And populations and societies are not stable. Some will last longer than others, but the changes will come. Will we know when the limits have been reached and act? Or will we be caught off guard, and realize we need to move someplace else? And where will we go?

I'm appalled when I hear politicians say that the most important questions facing our generation have to do with the marriage of the gays and how important it is to de-fund Planned Parenthood.

2 comments:

When I look at the historical water levels for Lake Mead and Lake Powell, I have to wonder about the sustainability of a growing population in the southwest.

Might we be headed for a long-term change in the climate regime, such as that which doomed the Hohokam and Anasazi? Those "bathtub rings" around Lake Powell and Lake Mead are warning signs that many people seem to ignore.

About Me

I am a teacher of geology at Modesto Junior College and former president of the National Association of Geoscience Teachers, Far Western Section. I have led field trips all over the western United States, and a few excursions overseas, but my homebase is the Sierra Nevada, the Great Valley, and the Coast Ranges of California.